A key element for the operation of a communications network is the availability of gateways to communications networks of other network operators. Presently such gateways are principally provided by operators of national telephone networks for routing calls to other national telephone networks. It can be expected that such gateways will also be found increasingly between telephone networks of private network operators as well as between telephone networks of public network operators.
The invention starts with the presently usual provision of a gateway between two national telephone networks, such as are described for example on pages 54 to 64 of the magazine "Trends in Telecommunications", 1992, Vol. 8, No. 1.
The gateways between two national telephone networks which are operated by two different network operators always comprise two switching facilities, one of which is assigned to one of the telephone networks and the other is assigned to the other telephone network. The two switching facilities are interconnected by a bearer channel and by signalling channels assigned to the bearer channel. Interworking functions for connections via the respective bearer channel to a gateway switching center of another network operator are performed in parallel to the exchange, and to establish the connection. Such interworking functions are for example a protocol conversion for different signalling methods in both telephone networks, functions for the provision of services of the other telephone network and the acquisition of communication events for the billing between network operators. These interworking functions are integral components of the respective gateway, which make it even possible to interconnect the two telephone networks through the respective gateway.
There is a problem in that the increasing number of network operators and telecommunications services made available in a telecommunications network further increase the complexity of the gateway switching facilities.